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Composition of Minor Ampullate Silk Makes Its Properties Different from Those of Major Ampullate Silk

Hiroyuki Nakamura1,2,3, Nobuaki Kono1,2, Masaru Mori1,2

  • 1Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan.

Biomacromolecules
|April 1, 2023
PubMed

Insights

Spider minor ampullate silk (MI-silk) differs from major ampullate silk (MA-silk) due to its protein composition. The study found that the absence of MaSp2 protein in MI-silk explains its unique water resistance properties compared to MA-silk.

Area of Science:

  • Biochemistry
  • Materials Science
  • Zoology

Background:

  • Spider silk, particularly minor ampullate silk (MI-silk), possesses unique mechanical properties and water resistance distinct from major ampullate silk (MA-silk).
  • The primary protein in MI-silk, minor ampullate spidroin (MiSp), has a known sequence, but the overall composition of MI-silk and its link to properties remain unclear.
  • Understanding these differences is crucial for biomaterials development and comprehending spider silk evolution.

Purpose of the Study:

  • To investigate the mechanical properties, water resistance, and proteome of MA-silk and MI-silk from two spider species, *Araneus ventricosus* and *Trichonephila clavata*.
  • To synthesize artificial fibers from major ampullate spidroins (MaSp1, MaSp2) and MiSp to compare their properties.
  • To elucidate the relationship between spider silk composition and its distinct mechanical and water resistance characteristics.

Main Methods:

  • Proteomic analysis of MA-silk and MI-silk from *Araneus ventricosus* and *Trichonephila clavata*.
  • Synthesis of artificial fibers using recombinant spidroins (MaSp1, MaSp2, MiSp).
  • Comparative analysis of mechanical properties and water resistance of natural and artificial silk fibers.

Main Results:

  • Proteomic analysis revealed that MI-silk is composed of MiSp, MaSp1, and spidroin constituting elements (SpiCEs).
  • MaSp2 protein was notably absent in the MI-silk proteome of both studied araneids.
  • Artificial fiber comparisons indicated that the presence of MaSp2 significantly influences water resistance.

Conclusions:

  • The composition of MI-silk includes MiSp, MaSp1, and SpiCEs, differing from MA-silk.
  • The absence of MaSp2 in MI-silk is a key factor contributing to its distinct properties.
  • MaSp2's presence is identified as the determinant for the difference in water resistance between MI-silk and MA-silk, offering insights for biomimetic material design.

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